The types and amount of plant raw materials which can be used as components in animal feed will often be limited by the ability of the animals to digest them. Feed enhancing enzymes are enzymes, usually of microbial origin, that by improving feed digestibility are able to increase the efficiency of its utilization.
When added to animal feed, feed enhancing enzymes improve the in vivo breakdown of plant cell wall material partly due to a reduction of the intestinal viscosity, whereby a better utilization of the plant nutrients by the animal is achieved. In this way the growth rate and/or feed conversion ratio (i.e. the weight of ingested feed relative to weight gain) of the animal becomes improved.
Xylanolytic enzymes (EC 3.2.1.8) are well known as feed enhancing enzymes. According to one theory, their primary effect is to reduce the viscosity of the feed, whereas another theory focuses on the xylanases increasing the availability of nutrients embedded in the plant cell wall. Thus WO 94/21785 describes xylanases derived from Aspergillus aculeatus and their use as animal feed additives, in particular in animal feed compositions containing high amounts of arabinoxylans and glucuronoxylans, e.g. feed containing cereals such as barley, wheat, rye or oats or maize.
WO 95/23514 describes a process for reducing the viscosity of a plant material and for separating plant material into desirable components, which process comprises treating the plant material with a xylanase preparation having a specific activity on water-soluble/water in-soluble pentosans. However, WO 95/23514 does not relate to mixtures of xylanases.